Methods for reducing cardiac valve regurgitation

ABSTRACT

The present invention relates to devices and methods for improving the function of a defective heart valve, and particularly for reducing regurgitation through an atrioventricular heart valve—i.e., the mitral valve and the tricuspid valve. For a tricuspid repair, the device includes an anchor deployed in the tissue of the right ventricle, in an orifice opening to the right atrium, or anchored to the tricuspid valve. A flexible anchor rail connects to the anchor and a coaptation element on a catheter rides over the anchor rail. The catheter attaches to the proximal end of the coaptation element, and a locking mechanism fixes the position of the coaptation element relative to the anchor rail. Finally, there is a proximal anchoring feature to fix the proximal end of the coaptation catheter subcutaneously adjacent the subclavian vein. The coaptation element includes an inert covering and helps reduce regurgitation through contact with the valve leaflets.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.15/296,887, filed Oct. 18, 2016, which is a continuation of U.S.application Ser. No. 13/895,572, filed May 16, 2013, now U.S. Pat. No.9,474,605, which claims priority under 35 U.S.C. § 119 to U.S.Provisional Application Ser. No. 61/647,973, filed May 16, 2012, and toU.S. Provisional Application Ser. No. 61/734,728, filed Dec. 7, 2012,the disclosures of which are expressly incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to devices and methods forimproving the function of a defective heart valve. The devices andmethods disclosed herein are particularly well adapted for implantationin a patient's heart for reducing regurgitation through a heart valve.

BACKGROUND OF THE INVENTION

The function of the heart may be seriously impaired if any of the heartvalves are not functioning properly. The heart valves may lose theirability to close properly due to e.g. dilation of an annulus around thevalve, ventricular dilation, or a leaflet being flaccid causing aprolapsing leaflet. The leaflets may also have shrunk due to disease,e.g. rheumatic disease, and thereby leave a gap in the valve between theleaflets. The inability of the heart valve to close properly can cause aleak backwards (i.e., from the outflow to the inflow side), commonlyreferred to as regurgitation, through the valve. Heart valveregurgitation may seriously impair the function of the heart since moreblood will have to be pumped through the regurgitating valve to maintainadequate circulation. Heart valve regurgitation decreases the efficiencyof the heart, reduces blood circulation, and adds stress to the heart.In early stages, heart valve regurgitation leaves a person fatigued orshort of breath. If left unchecked, the problem can lead to congestiveheart failure, arrhythmias or death.

Heart valve disease, such as valve regurgitation, is typically treatedby replacing or repairing the diseased valve during open-heart surgery.However, open-heart surgery is highly invasive and is therefore not anoption for many patients. For high-risk patients, a less-invasive methodfor repair of heart valves is considered generally advantageous.

Accordingly, there is an urgent need for an alternative device andmethod of use for treating heart valve disease in a minimally invasiveprocedure that does not require extracorporeal circulation. It isespecially desirable that embodiments of such a device and method becapable of reducing or eliminating regurgitation through a tricuspidheart valve. It is also desirable that embodiments of such a device andmethod be well-suited for treating a mitral valve. It is also desirablethat such a device be safe, reliable and easy to deliver. It is alsodesirable that embodiments of such a device and method be applicable forimproving heart valve function for a wide variety of heart valvedefects. It is also desirable that embodiments of such a device andmethod be capable of improving valve function without replacing thenative valve. The present invention addresses this need.

SUMMARY OF THE INVENTION

The present invention relates generally to devices and methods forimproving the function of a defective heart valve. The devices andmethods disclosed herein are particularly well adapted for implantationin a patient's heart for reducing regurgitation through a heart valve.The devices and methods disclosed herein are particularly useful inreducing regurgitation through the two atrioventricular (AV) valves,which are between the atria and the ventricles—i.e., the mitral valveand the tricuspid valve.

In one embodiment, the device comprises: an anchor to deploy in thetissue of the right ventricle, a flexible anchor rail connected to theanchor, a coaptation element that rides over the anchor rail, a catheterattached to the proximal end of the coaptation element, a lockingmechanism to fix the position of the coaptation element relative to theanchor rail, and a proximal anchoring feature to fix the proximal end ofthe coaptation catheter subcutaneously in the subclavian vein.

In another particular embodiment, the coaptation element consists of ahybrid structure: a series of a plurality (preferably three or more)flexible metallic struts to define a mechanical frame structure or acompressible biocompatible material, and a covering of pericardium orsome other biocompatible material to provide a coaptation surface aroundwhich the native leaflets can form a seal. The flexible struts desirablyattach to a catheter shaft on their proximal and/or distal ends, andcollapse into a smaller diameter in order to be delivered through a lowprofile sheath. In particular, the struts attach on one end or both to acatheter shaft, and are complete or interrupted, they typically extendthe length of the element, extend out or inwards, and may be discretestruts or a more connected mesh. The mechanical frame typically expandsto the larger shape passively upon exiting a protective sheath via shapememory properties (e.g. Nitinol), but could also be expanded vialongitudinal compression of the catheter, a shape memory balloon or someother external force. Additionally, the coaptation element can be anopen or closed structure, any biocompatible material and framework thatallows for compressibility for delivery and expands either actively orpassively upon delivery, can be various shapes, and can be a passive oractive element that is responsive to the cardiac cycle to change shapesto accommodate the regurgitant orifice.

In accordance with a preferred embodiment, a heart valve coaptationsystem for reducing regurgitation through the valve comprises a flexiblerail having a ventricular anchor on the distal end thereof adapted toanchor into tissue within a ventricle. A delivery catheter has a lumenthrough which the flexible rail passes, and a coaptation member fixed ona distal end of the delivery catheter has a bell-shaped cover with afirst end open and a flexible inner support holding the first end open.Finally, a locking collet on the delivery catheter secures the axialposition of the coaptation member and delivery catheter on the flexiblerail.

The locking collet preferably includes a pair of internally threadedtubular grips each fixed to one of two separate sections of the deliverycatheter and engaging a common externally threaded tubular shaft member.The tubular grips act on a wedge member interposed between at least oneof the grips and the flexible rail to securing the axial position of thecoaptation member and delivery catheter on the flexible rail. The firstend of the bell-shaped cover of the coaptation member may be on a distalor ventricular side thereof, or on the proximal or atrial side. Thesecond end of the bell-shaped cover may have flow through openings tohelp avoid blood stagnation. The flexible inner support may comprise aflexible frame with struts emanating from a central collar and engagingthe first end of the bell-shaped cover, or with struts that extendsubstantially the length of the bell-shaped cover. Alternatively, theflexible inner support comprises a compressible foam membersubstantially filling the cover. The cover may formed of polycarbonateurethane, or may be bioprosthetic tissue.

Another exemplary embodiment of a heart valve coaptation system forreducing regurgitation through the valve again includes a flexible railhaving a ventricular anchor on the distal end thereof adapted to anchorinto tissue within a ventricle, and a delivery catheter having a lumenthrough which the flexible rail passes. A coaptation member fixed on adistal end of the delivery catheter has a smooth outer cover with acompressible foam inner support. A locking collet is provided on thedelivery catheter for securing the axial position of the coaptationmember and delivery catheter on the flexible rail. Alternatively, thecoaptation member has an outer cover of polycarbonate urethane with aflexible inner support holding the cover outward from the deliverycatheter.

In either of the two previous systems, the ventricular anchor maycomprises two separate anchors that cooperate to secure the flexiblerail of the flexible rail to the ventricle tissue. In one version, thecover is tubular with both ends open, and if not made of polycarbonateurethane the cover is made of bioprosthetic tissue. If the flexibleinner support is a compressible foam member it may substantially fillthe cover and be an open cell foam that permits blood flow therethrough.The flexible inner support may also comprise a flexible frame withstruts that extend substantially the length of the cover between thecompressible foam member and the cover. Alternatively, the flexibleframe has struts emanating from a central collar and engaging the insideof the cover. In one embodiment, wherein the cover is tubular with bothends open, while in another the cover is bell-shaped with a distal orventricular side being open and a proximal or atrial side being closed.Alternatively, the cover is bell-shaped with both ends being closed.

A further understanding of the nature and advantages of the presentinvention are set forth in the following description and claims,particularly when considered in conjunction with the accompanyingdrawings in which like parts bear like reference numerals.

BRIEF DESCRIPTION OF THE DRAWINGS

To further clarify various aspects of embodiments of the presentdisclosure, a more particular description of the certain embodimentswill be made by reference to various aspects of the appended drawings.It is appreciated that these drawings depict only typical embodiments ofthe present disclosure and are therefore not to be considered limitingof the scope of the disclosure. Moreover, while the figures may be drawnto scale for some embodiments, the figures are not necessarily drawn toscale for all embodiments. Embodiments of the present disclosure will bedescribed and explained with additional specificity and detail throughthe use of the accompanying drawings.

FIG. 1A is a cutaway view of the human heart in a diastolic phaseshowing introduction of an anchoring catheter into the right ventricleas a first step in deploying a device of the present application forreducing tricuspid valve regurgitation;

FIG. 1B is a cutaway view of the human heart in a systolic phase showingretraction of the anchoring catheter after installing a device anchor atthe apex of the right ventricle;

FIGS. 2A-2C are detailed views of installation of an exemplary deviceanchor by the anchoring catheter;

FIGS. 3A and 3B are sectional views of the right atrium and ventriclethat illustrate deployment of a regurgitation reduction device includinga delivery catheter advanced along an anchor rail to position a coaptingelement within the tricuspid valve;

FIGS. 4A-4C are perspective and longitudinal sectional views of alocking collet shown proximally positioned on the catheter of FIGS. 3Aand 3B that is used to fix the position of the delivery catheter andcoapting element relative to the anchor rail;

FIG. 5 is a broader view of the final configuration of the regurgitationreduction device of the present application with a coapting elementpositioned within the tricuspid valve and a proximal length of thedelivery catheter including the locking collet shown exiting thesubclavian vein to remain implanted subcutaneously;

FIGS. 6A and 6B are assembled and exploded elevational views of anexemplary coapting element having an inner strut frame and tissuepartially covering an atrial end of the coapting element;

FIGS. 7A and 7B are assembled and exploded elevational views of anothercoapting element having an inner strut frame and tissue partiallycovering a ventricular end of the coapting element;

FIG. 8 is an assembled elevational view of a still further coaptingelement having a tissue cover on the atrial end and cantilevered strutsextending from the atrial end within the tissue cover;

FIGS. 9A-9C are assembled elevational and atrial end views of anothercoapting element with a tissue cover and cantilevered struts extendingfrom the ventricular end thereof;

FIGS. 10A-10B are assembled elevational and ventricle end views of acoapting element having an atrial end tissue cover and an inner strutconfiguration with some struts extending the full length of the coaptingelement and some cantilevered from the atrial end;

FIGS. 11A-11B are views of a coapting element much like that shown inFIGS. 10A-10B but with the tissue cover and struts extending from theventricular end;

FIG. 12 is an elevational view of a coaptation element much like FIG.6A, but with a modified coupling structure on the proximal end of aninner mechanical frame that permits a delivery catheter to be snap fitthereto, and FIG. 12A is an enlargement of the proximal coupling;

FIG. 13 is an enlarged view of the proximal coupling between thedelivery catheter and the mechanical frame of FIG. 12;

FIGS. 14A-14C are schematic views of various constructions ofthree-strut/three-panel coapting elements disclosed herein;

FIG. 15 is a schematic view of the construction of a two-strut/two-panelcoapting element;

FIG. 16 is a schematic diagram of a representative coapting element anda pair of native tissue leaflets indicating certain key dimensions usedin constructing the coapting element;

FIGS. 17A-17C are assembled and exploded views of a coapting elementhaving a three-strut frame, a tubular tissue or other materialscovering, and an inner compressible biocompatible material such as afoam;

FIG. 18 is an elevational view of the coapting element of FIGS. 17A-17Cbeing inserted through a constrictor sleeve used for reducing thediameter of the coapting element during delivery into the body;

FIGS. 19 and 20 are assembled and exploded views, respectively, of analternative coapting element comprising a bell-shaped polymer memberheld open at one end via a multi-strut frame;

FIG. 21 is a partial cutaway perspective view of a coapting elementsimilar to that shown in FIG. 19, but having a multi-strut frame whichis positioned within the bell-shaped polymer member;

FIGS. 22A-22G illustrates an exemplary assembly sequence for thecoapting element of FIGS. 19 and 21;

FIG. 23A is a perspective view of another coapting element of thepresent application wherein an outer biocompatible tubular cover mountsto an internal multiple strut frame and encloses a compressible membersuch as foam therein, and FIG. 23B is an end view thereof;

FIGS. 24A-24C and 25A-25B illustrate a number of components thatcomprise the coapting element of FIG. 23A;

FIGS. 26A and 26B are assembled and exploded views of a still furthercoapting element of the present application having an outer tubularcover surrounding a porous compressible member;

FIGS. 27A and 27B are assembled and exploded views of a coapting elementsimilar to that in FIGS. 26 and 27 but wherein a ventricular end of theouter cover is closed;

FIG. 28 is an assembled view of a coapting element with an outer coversurrounding an inner compressible member and with a perforated innercatheter for removing air from the compressible member, shown,respectively, in FIGS. 29A and 29B;

FIG. 30 is a perspective view of a coapting element having an outerbell-shaped cover with a plurality of flow through holes on an otherwiseclosed atrial end, and FIGS. 31A and 31B show alternative hole patterns;

FIGS. 32A-32B are sectional views of the heart illustrating aregurgitation reduction device positioned in the right atrium/rightventricle and having a three-sided frame as a coaptation element;

FIGS. 33A and 33B are elevational and end views of the coaptationelement from FIGS. 32A-32B;

FIGS. 34 and 35 are radial section views through the coaptation elementof FIG. 33A showing two different possible configurations, one hollowand one filled with a compressible material;

FIGS. 36A and 36B are sectional views of the heart in diastole andsystole, respectively, showing a regurgitation reduction device which ismounted to the apex of the right ventricle with a spring that permits acoapting element to move in and out of the right ventricle in accordancewith the cardiac cycle;

FIGS. 37 and 38 are views of alternative anchoring members utilizingcoil springs;

FIG. 39 is a partial sectional view of an alternative anchoring devicehaving concentric corkscrew anchors, while FIGS. 39A-39C illustratesteps in installation of the anchoring device;

FIGS. 40 and 41 are views of still further anchoring members of thepresent application;

FIGS. 42A and 42B show operation of a centering balloon that helpsensure proper positioning of an anchoring member at the apex of theright ventricle;

FIG. 43 illustrates a step in directing an anchoring catheter to theapex of the right ventricle using an L-shaped stabilizing cathetersecured within a coronary sinus;

FIG. 44 schematically illustrates a stabilizing rod extending laterallyfrom a regurgitation reduction device delivery catheter in the rightatrium above the tricuspid valve;

FIG. 45 illustrates an adjustable stabilizing rod mounted on thedelivery catheter and secured within the coronary sinus;

FIG. 46 illustrates an alternative delivery catheter having a pivotjoint just above the coapting element;

FIGS. 47A and 47B show two ways to anchor the delivery catheter to thesuperior vena cava for stabilizing the coapting element;

FIGS. 48A and 48B show a regurgitation reduction device having pullwires extending therethrough for altering the position of the coaptingelement within the tricuspid valve leaflets;

FIG. 49 shows a regurgitation reduction device anchored with stents inboth the superior and inferior vena cava and having rods connecting thestents to the atrial side of the coapting element;

FIGS. 50A-50C are schematic views of a coapting element mounted forlateral movement on a flexible delivery catheter that collapses andallows rotation for seating centrally in the valve plane even if thedelivery catheter is not central; and

FIGS. 51A and 51B are radial sectional views through the coaptingelement as seen in FIGS. 50A and 50B, respectively.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description refers to the accompanying drawings, whichillustrate specific embodiments of the invention. Other embodimentshaving different structures and operation do not depart from the scopeof the present invention.

Exemplary embodiments of the present disclosure are directed to devicesand methods for improving the function of a defective heart valve. Itshould be noted that various embodiments of coapting elements andsystems for delivery and implant are disclosed herein, and anycombination of these options may be made unless specifically excluded.For example, any of the coapting elements disclosed may be combined withany of the flexible rail anchors, even if not explicitly described.Likewise, the different constructions of coapting elements may be mixedand matched, such as combining any tissue cover with any inner flexiblesupport, even if not explicitly disclosed. In short, individualcomponents of the disclosed systems may be combined unless mutuallyexclusive or otherwise physically impossible.

FIGS. 1A and 1B are cutaway views of the human heart in diastolic andsystolic phases, respectively. The right ventricle RV and left ventricleLV are separated from the right atrium RA and left atrium LA,respectively, by the tricuspid valve TV and mitral valve MV; i.e., theatrioventricular valves. Additionally, the aortic valve AV separates theleft ventricle LV from the ascending aorta (not identified) and thepulmonary valve PV separates the right ventricle from the pulmonaryartery (also not identified). Each of these valves has flexible leafletsextending inward across the respective orifices that come together or“coapt” in the flowstream to form the one-way fluid occluding surfaces.The regurgitation reduction devices of the present application areprimarily intended for use to treat the atrioventricular valves, and inparticular the tricuspid valve. Therefore, anatomical structures of theright atrium RA and right ventricle RV will be explained in greaterdetail, though it should be understood that the devices described hereinmay equally be used to treat the mitral valve MV.

The right atrium RA receives deoxygenated blood from the venous systemthrough the superior vena cava SVC and the inferior vena cava IVC, theformer entering the right atrium above, and the latter from below. Thecoronary sinus CS is a collection of veins joined together to form alarge vessel that collects deoxygenated blood from the heart muscle(myocardium), and delivers it to the right atrium RA. During thediastolic phase, or diastole, seen in FIG. 1A, the venous blood thatcollects in the right atrium RA is pulled through the tricuspid valve TVby expansion of the right ventricle RV. In the systolic phase, orsystole, seen in FIG. 1B, the right ventricle RV collapses to force thevenous blood through the pulmonary valve PV and pulmonary artery intothe lungs. During systole, the leaflets of the tricuspid valve TV closeto prevent the venous blood from regurgitating back into the rightatrium RA. It is during systole that regurgitation through the tricuspidvalve TV becomes an issue, and the devices of the present applicationare beneficial.

Regurgitation Reduction System:

FIGS. 1A and 1B show introduction of an anchoring catheter 20 into theright ventricle as a first step in deploying a device of the presentapplication for reducing tricuspid valve regurgitation. The anchoringcatheter 20 enters the right atrium RA from the superior vena cava SVCafter having been introduced to the subclavian vein (see FIG. 5) usingwell-known methods, such as the Seldinger technique. More particularly,the anchoring catheter 20 preferably tracks over a pre-installed guidewire (not shown) that has been inserted into the subclavian vein andsteered through the vasculature until it resides at the apex of theright ventricle. The physician advances the anchoring catheter 20 alongthe guide wire until its distal tip is touching the ventricular apex, asseen in FIG. 1A.

FIG. 1B shows retraction of a sheath 22 of the anchoring catheter 20after installing a device anchor 24 at the apex of the right ventricleRV. The sheath 22 has desirably been removed completely from thepatient's body in favor of the second catheter, described below.

First, a detail explanation of the structure and usage of an exemplarydevice anchor 24 will be provided with reference to FIGS. 2A-2C. FIG. 2Ais an enlargement of the distal end of the anchoring catheter sheath 22in the position of FIG. 1A. The device anchor 24 is seen within thesheath 22 positioned just within the distal end thereof. The deviceanchor 24 attaches to an elongated anchor rail 26, which in someversions is constructed to have good capacity for torque. For instance,the anchor rail 26 may be constructed as a braided wire rod, or cable.

In FIG. 2B, the catheter sheath 22 is shown being retracted proximally,while the device anchor 24 and anchor rail 26 are expelled distallytherefrom. The exemplary device anchor 24 includes a plurality ofcircumferentially distributed and distally-directed sharp tines or barbs28 that pierce the tissue of the ventricular apex. The barbs 28 are heldin a stressed configuration within the sheath 22, and are provided withan outward elastic bias so that they curl outward upon release from thesheath. Desirably the barbs 28 are made of a super-elastic metal such asNitinol. The outward curling of the barbs 28 can be seen in both FIGS.2B and 2C, the latter showing the final relaxed configuration of thebarbs. The operation to embed the device anchor 24 may be controlledunder visualization, such as by providing radiopaque markers in andaround the device anchor 24 and distal end of the catheter sheath 22.Certain other devices described herein may be used to help position thedevice anchor 24 at the ventricular apex, as will be described. Althoughthe particular device anchor 24 shown in FIGS. 2A-2C is consideredhighly effective, other anchors are contemplated, such as shown anddescribed below, and the application should not be considered limited toone type or another.

To facilitate central positioning of the anchor rail 26 duringdeployment the device is implanted with the assistance of a fluoroscope.For example, after properly positioning the patient so as to maximizethe view of the target annulus, for example the tricuspid annulus, apigtail catheter is placed in the right ventricle and contrast injected.This allows the user to see a clear outline of the annulus and the rightventricle. At this point, a frame of interest is selected (e.g., endsystole) in which the annulus is clearly visible and the annulus toventricular apex distance is minimized. On the monitor, the outline ofthe right ventricle, the annulus, and the pulmonary artery are traced.The center of the annulus is then identified and a reference line placed90° thereto is drawn extending to the right ventricular wall. Thisprovides a clear linear target for anchoring. In a preferred embodiment,the anchor 24 is preferably located in the base of the ventricle betweenthe septum and the free wall.

Aligning the anchor rail 26 in this manner helps center the eventualpositioning of a coapting element of the system within the tricuspidleaflets. If the coapting element is offset to the anterior or posteriorside, it may get stuck in the tricuspid valve commissures resulting inleakage in the center of the valve. An alternative method is to place adevice such as a Swan Ganz catheter through the right ventricle and intothe pulmonary artery to verify that the viewing plane is parallel to theanterior/posterior viewing plane. Addition of a septal/lateral view onthe fluoroscope may be important to center the anchor in patients thathave a dilated annulus and right ventricle.

FIGS. 3A and 3B illustrate deployment of a regurgitation reductiondevice 30 including a delivery catheter 32 advanced along the anchorrail 26 to position a coapting element 34 within the tricuspid valve TV.The coapting element 34 fastens to a distal end of the delivery catheter32, both of which slide along the anchor rail 26, which has beenpreviously positioned as described above. Ultimately, as seen in FIG.3B, the coapting element 34 resides within the tricuspid valve TV, theleaflets of which are shown closed in systole and in contact with thecoapting element. Likewise, the delivery catheter 32 remains in the bodyas seen in FIGS. 3B and 5, and the prefix “delivery” should not beconsidered to limit its function. A variety of coapting elements aredescribed herein, the common feature of which is the goal of providing aplug of sorts within the heart valve leaflets to mitigate or otherwiseeliminate regurgitation. In the illustrated embodiment, the coaptingelement 34 includes an inner strut structure partly surrounded bybioprosthetic tissue, as will be described in more detail below.

A locking mechanism is provided on the regurgitation reduction device 30to lock the position of the coapting element 34 within the tricuspidvalve TV and relative to the fixed anchor rail 26. For example, alocking collet 40 along the length of the delivery catheter 32 permitsthe physician to selectively lock the position of the delivery catheter,and thus the connected coapting element 34, on the anchor rail 26. Thereare of course a number of ways to lock a catheter over a concentricguide rail, and the application should not be considered limited to theillustrated embodiment. For instance, rather than a locking collet 40, acrimpable section such as a stainless steel tube may be included on thedelivery catheter 32 at a location near the skin entry point and spacedapart from the location of the coapting element 34. The physician needonly position the coapting element 34 within the leaflets, crimp thecatheter 32 onto the anchor rail 26, and then sever both the catheterand rail above the crimp point.

Details of the exemplary locking collet 40 are seen in FIGS. 4A-4C. Thecollet 40 includes two short tubular grips 42 a, 42 b that areinternally threaded and engage a common externally threaded tubularshaft member 44. The delivery catheter 32 is interrupted by the collet40, and free ends of the catheter fasten within bores provided inopposite ends of the grips 42 a, 42 b. As seen in FIG. 4B, the anchorrail 26 extends through the middle of the locking collet 40, thuscontinuing the length of the delivery catheter 32. Furthermore, when thegrips 42 a, 42 b are separated from each other as seen in FIGS. 4A and4B, the anchor rail 26 slides freely through the locking collet 40.

An inner, generally tubular wedge member 46 is concentrically positionedbetween the shaft member 44 and the anchor rail 26. One or both ends ofthe wedge member 46 has a tapered surface 48 (see FIG. 4C) thatinteracts with a similarly tapered inner bore of the surrounding tubulargrip 42 a, 42 b. The wedge member 46 features a series of axial slotsextending from opposite ends which permit its diameter to be reducedfrom radially inward forces applied by the surrounding grips 42 a, 42 band shaft member 44. More particularly, FIG. 4C shows movement of thetwo grips 42 a, 42 b toward each other from screwing them together overthe threaded shaft member 44. Desirably, outward ribs or other suchfrictional enhancers are provided on the exterior of both of the grips42 a, 42 b to facilitate the application of torque in the often wetsurgical environment. Axial movement of the tapered inner bore of one orboth of the grips 42 a, 42 b forces inward the tapered surface 48 of thewedge member 46, and also the outer ends of the shaft member 44. Inother words, screwing the grips 42 a, 42 b together cams the shaftmember and a wedge member 46 inward. The dimensions are such that whenthe two grips 42 a, 42 b come together, the inward force applied by thewedge member 46 on the anchor rail 26 is sufficient to lock the deliverycatheter 32 and anchor rail.

Now with reference to FIG. 5, the entire regurgitation reduction device30 can be seen extending from the apex of the right ventricle RV upwardthrough the superior vena cava SVC and into the subclavian vein SV. Aproximal length of the delivery catheter 32 including the locking collet40 exits the subclavian vein SV through a puncture and remains implantedsubcutaneously; preferably coiling upon itself as shown. In theprocedure, the physician first ensures proper positioning of thecoapting element 34 within the tricuspid valve TV, then locks thedelivery catheter 32 with respect to the anchor rail 26 by actuating thelocking collet 40, and then severs that portion of the delivery catheter32 that extends proximally from the locking collet. The collet 40 and/orcoiled portion of the delivery catheter 32 may be sutured or otherwiseanchored in place to subcutaneous tissues outside the subclavian veinSV. It is also worth noting that since the delivery catheter 32 slideswith respect to the anchor rail 26, it may be completely removed towithdraw the coapting element 34 and abort the procedure—either duringor after implantation. The implant configuration is similar to thatpracticed when securing a pacemaker with an electrode in the rightatrium muscle tissue and the leads extending to the associated pulsegenerator placed outside the subclavian vein. Indeed, the procedure maybe performed in conjunction with the implant of a pacing lead.

Coapting Elements:

As mentioned, a number of different coapting elements are described inthe present application. Indeed, the present application provides aplurality of solutions for preventing regurgitation in atrioventricularvalves, none of which should be viewed as necessarily more effectivethan another. For example, the choice of coapting element depends partlyon physician preference, partly on anatomical particularities, partly onthe results of clinical examination of the condition of the patient, andother factors.

One broad category of coapting element that is disclosed herein and hasbeen subject to testing is a flexible mechanical frame structure atleast partially covered with bioprosthetic tissue. The inner framestructure is flexible enough to react to the inward forces imparted bythe closing heart valve leaflets, and therefore undergo a shape changeto more completely coapt with the leaflets, thus reducing regurgitantjets. The bioprosthetic tissue covering helps reduce materialinteractions between the native leaflets and the inner mechanical frame.As mentioned above, the regurgitation reduction device can beeffectively deployed at either the tricuspid or mitral valves, theformer which typically has three leaflet cusps defined around theorifice while the latter has just two. The tissue-covered mechanicalframe structure thus represents an effective co-optation element forboth valves by providing a highly flexible structure which issubstantially inert to tissue interactions.

An exemplary embodiment of this so-called “Flexible Bell CoaptationElement” consists of a pericardial tissue (or a biocompatible flexiblematerial) that is cut and sewn to create a sac/bell shape that is ableto hold liquid (blood). One embodiment is designed to sit in the valveplane such that the open end is towards the atrium and the closedportion towards the ventricle. Therefore during diastole, blood flowsinto the coaptation element and fills the sac, conversely during systoleas the native leaflets begin to close and contact the coaptationelement, the pressure and blood flow work to decrease the size of thecoaptation element by pushing blood out of the top edge sufficientlywhile still creating a seal.

Variations on the system include various design shapes at theventricular end that is closed such as a half circle, triangle, ellipseor the like. Additionally sutures on the closed end as well as axiallyalong the coaptation element better define how the element closes frominteraction with the native leaflets. Lastly a more rigid support suchas cloth, wire or other material could be sutured along the open atrialseated edge to ensure that the design remained open during the cardiaccycle. These principles apply equally to coapting elements that are opento the ventricle and closed to the atrium.

FIGS. 6A and 6B are assembled and exploded elevational views of anexemplary coapting element 34 having an inner strut frame 50 and atissue cover 52 partially covering an atrial end of the coaptingelement. For the sake of uniformity, in these figures and others in theapplication the coapting elements are depicted such that the atrial endis up, while the ventricular end is down. These directions may also bereferred to as “proximal” as a synonym for up or the atrial end, and“distal” as a synonym for down or the ventricular end, which are termsrelative to the physician's perspective.

A small portion of the delivery catheter 32 is seen at the proximal endof the coapting element 34. In one embodiment, a short tubular collar 54fastens to the distal end of the delivery catheter 32 and providesstructure to surround the proximal ends of a plurality of struts 56 thatform the strut frame 50. A second tubular collar 58 holds together thedistal ends of the struts 56 and attaches to a small ferrule 60 having athrough bore that slides over the anchor rail 26. Each of the struts 56has proximal and distal ends that are formed as a part of (orconstrained within) these collars 54, 58 and a mid-portion that arcsradially outward to extend substantially parallel to the axis of thecoapting element 34. The frame shape is thus a generally elongated oval.In the illustrated embodiment, there are six struts 56 in the frame 50,although more or less could be provided. The struts 56 are desirablyformed of a super-elastic material such as Nitinol so as to have aminimum amount of rigidity to form the generally cylindrical outline ofthe frame but maximum flexibility so that the frame deforms from theinward forces imparted by the heart valve leaflets.

The tissue cover 52 preferably comprises one or more panels 61 ofbioprosthetic tissue sewn around the struts 56 of the frame 50. A singleaxial seam 62 is shown in the figures, though as will be explained belowthe cover 52 is typically formed of two or three panels sewn togetherwith a matching number of seams. The tissue cover 52 may be formed of avariety of xenograft sheet tissue, though bovine pericardial tissue isparticularly preferred for its long history of use in cardiac implants,physical properties and relative availability. Other options are porcineor equine pericardium, for example. In the embodiment illustrated inFIGS. 6A-6C, the tissue cover 52 has a proximal end that is closed tofluid flow, and a distal end 64 that is open; thus, the cover resemblesa bell shape. Desirably, the axial length of the cover 52 extends fromthe proximal collar 54 approximately three-quarters of the way down tothe distal collar 58, to the end of the flat section of the device. Asmentioned above, the open bell shape desirably facilitates functioningof the coapting element. Namely, during diastole, blood flows around thecoaptation element 34, while during systole, as the native leafletsclose and contact the coaptation element, the pressure and blood flowwork to fill the interior of the coaptation element by pushing blood in,the interior of the coaptation element is at the same pressure as the RVand a seal is created. These phases of the cardiac cycle are common toboth the tricuspid and mitral valves. Generally the coaptation elementsthat are closed on the atrial side and open to the ventricular side moveessentially like a parachute—filling in systole, and blood flowingaround without collapse in diastole.

FIGS. 7A and 7B illustrate an alternative coapting element 68 much likethe coapting element 34 described above, having an inner strut frame 70and a tissue cover 72 partially covering a ventricular end of thecoapting element, which functions like a flexible cup to blockregurgitation. Indeed, the structure of the coapting element 68 isidentical to that described above except for two features—the tissuecover 72 is closed at the ventricular end, but open at the atrial end,and there are three elongated struts 74 extending between and capturedby upper and lower collars 76 a, 76 b. The number of struts can vary forboth designs, though 6 or 9 struts are currently contemplated. Onceagain, the delivery catheter 32 fixes to the upper collar 76 a, whilethe anchor rail 26 extends through the entire structure and slidesthrough the lower collar 76 b. After implant of the upwardly openingcoapting element 68, blood will close the tricuspid valve leafletsduring systole around the tissue cover 72 (as in FIG. 3B) withrelatively little resistance from the coapting element. Conversely,during diastole blood flows downward from the right atrium to the rightventricle around the coapting element 68, and though some will flow intoand inflate the tissue cover 72, its size will not significantly impedefilling of the right ventricle.

FIG. 8 is an assembled elevational view of a still further coaptingelement 80 having a tissue cover 82 on the atrial end (open to theventricle) and cantilevered struts (not visible) extending from theatrial end within the tissue cover. That is, the coapting element 80 issimilar to coapting element 34 from FIG. 6A, though instead of anoval-shaped mechanical frame within the tissue cover 82, the struts aresimply fixed to and cantilevered from an atrial collar 86. As before,the delivery catheter 30 attaches to the collar 86, and the entireassembly slides over the anchor rail 26.

FIGS. 9A-9C illustrate another coapting element 90 with a tissue cover92 open to the atrial end and cantilevered struts 94 extending from acollar 96 at the ventricular end. In other words, the coapting element90 is essentially an inverse to the coapting element 80 of FIG. 8. FIG.9B shows the coapting element 90 looking down from the atrial side in anexpanded configuration of the tissue cover 92 in diastole when bloodflows downward from the right atrium to the right ventricle and inflatesthe cover. In FIG. 9C, systolic pressures in the right ventricle closethe tricuspid valve leaflets around the coapting element 90, thuscausing it to collapse and force blood from the interior of the tissuecover 92 into the right atrium. It will be noticed that some of thestruts 94 collapse inward more than others, reflecting the uneven inwardforces imparted by the tricuspid leaflets. Struts that do not deform somuch remain bowed outward toward the valve commissures. The diagram isschematic and shown with three struts moving all the way in and threeremaining in approximately the same position. However, it will beunderstood that the compacted shape of the coapting element 90 will berelatively random, and may change from cycle to cycle.

FIGS. 10A-10B shows a still further embodiment of a coapting element 100having an atrial end tissue cover 102, similar to that shown in FIGS. 6Aand 8, but with an inner strut configuration with some struts 104extending the full length of the coapting element and some struts 106cantilevered from the atrial end, in particular from an atrial collar108. The staggered nature of the full-length struts 104 and cantileveredstruts 106 is seen from the ventricular end in FIG. 10B. With thisconfiguration, segments of the coapting element 100 having thecantilevered struts 106 are more inwardly flexible than the segmentshaving the full-length of struts 104, which provides a collapsiblestructure that is someone more flexible than the embodiment of FIG. 6Abut more rigid than the embodiment shown in FIG. 8.

FIGS. 11A-11B illustrate a similar coapting element 110 as in FIGS.10A-10B, but with the tissue cover 112 and struts 114, 116 extendingfrom the ventricular end, preferably from a ventricular collar 118.

Many of the coapting elements described herein benefit from the use of abioprosthetic tissue covering. Often, such tissue coverings must bestored in a preservative solution, such as glutaraldehyde, for longperiods, which may be deleterious to the material of the syntheticcomponents of the overall device. Accordingly, any of the bioprosthetictissue coapting elements described herein should be stored separatelyfrom other components that could be damaged from long-term storage andpreservative solution, such as polymer catheters and the like.

FIGS. 12, 12A, and 13 illustrate one such arrangement where a coaptingelement 120 has a proximal coupling sleeve 121 that can be snap fit to adistal coupler 122 of a delivery catheter. More particularly, FIGS. 12Aand 13 show small oval windows 123 in the coupler 122 which receivedoutwardly biased spring tabs 124 on a tubular hub 125 of the couplingsleeve 121. At the time of the surgical procedure, a technician in theoperating room removes the bioprosthetic coapting element 120 from itsliquid-filled storage container, typically rinsing it, and then joinsthe catheter coupler 122 to the proximal sleeve 121 by pushing the twotogether until the tabs 124 spring outward through the windows 123. Itshould be also noted that the internal mechanical frame structureincluding the flexible struts 126 are formed in one homogenous piecewith the tubular hub 125 of the coupling sleeve 121, which improveslong-term integrity of the entire structure.

As mentioned above, a preferred construction of the mechanicalframe/tissue cover coapting elements includes a plurality of panels ofbioprosthetic tissue sewn to the inner struts. FIGS. 14A-14Cschematically illustrate several different configurations ofthree-strut/three-panel coapting elements in this regard. Moreparticularly, FIG. 14A shows the three panels 128 of bioprosthetictissue having generally rectangular configurations except for theirlower ends which are pointed. A view of the finished coapting elementfrom its open end is seen to the right wherein all of the six struts 130are cantilevered from the closed end. In a preferred construction, clothpieces 132 are first sewn around some or all of the struts 130.Separately, the three tissue panels 128 are sewn to each other to form atubular structure, and such that the flaps of the longitudinal seamsface to the inside of the tube. This may require first sewing the seamson the outside and then inverting the tubular structure. Subsequently,the tubular structure of the three panels 128 is sewn to the clothpieces 132 preassembled around some or all of the struts. In theillustrated embodiment, there are three panels 128 and thus three seams,so that only three cloth pieces 132 are used around three of the sixstruts 130. Finally, the pointed lower ends of the tissue panels 128 aresewn together to close off that end, whether it be the atrial orventricular side.

FIG. 14B is much the same as the construction of FIG. 14A; however themechanical frame structure has six struts 134 that extend the fulllength of the coapting elements with none of them cantilevered. Finally,FIG. 14C shows another similar embodiment wherein there are three struts136 extending the full length of the coapting element, with threeintermediate struts 138 cantilevered from the closed end of themechanical frame.

FIG. 15 schematically illustrates components in the construction of atwo-strut/two-panel coapting element. Because of the modifiedthree-dimensional shape, the lower ends of the panels 140 are curvedrather than pointed. The two struts 142 extend the full length of thecoapting element and are diametrically opposed. This coapting elementthus has a much more two-dimensional shape, though the open end of thetissue cover permits the structure to be inflated when the element ispressurized from the open end.

FIG. 16 is a schematic diagram of a pair of native tissue leaflets 144indicating certain key dimensions used in constructing the coaptingelement. The inquiry seeks to determine a preferred height of thecoapting element, or at least the height of the leaflet contactingsurface of the elements. It is known that the length of heart valveleaflets are often mismatched, and the dimension LM indicates theleaflet mismatch as a distance along the axis of the valve. An axialdimension of a coapting element that fits within these two mismatchedleaflets will therefore have a minimum height that starts at the tip ofthe longer leaflet and extends upward approximately twice the leafletmismatch LM dimension, indicated as H_(min). To avoid inserting toolarge a structure between the leaflets, a dimension H_(max) extends fromapproximately the plane of the annulus of the leaflets (i.e., where theyattach to the surrounding wall) down to a distance into the ventriclewhich is centered at the center of the dimension H_(min). The leafletexcursion LE reflects the length along which the leaflets are known tocontact the coapting devices. That is, the leaflets first hit the deviceand then move down with the contraction of the heart. There musttherefore be enough surface length or leaflet excursion LE for theleaflets to maintain contact. In general, the axial dimension of thecoapting element should ensure enough coaptation length to accommodateleaflet mismatch and leaflet excursion without protruding too much intothe ventricle or atrium.

FIGS. 17A-17C illustrate another coapting element 150 having athree-strut mechanical frame 152, a tubular tissue covering 154, and aninner foam cylinder 156. The foam cylinder 156 has a through bore forreceiving a delivery catheter 158. Three struts 160 are retained by apair of end collars 162 secured to the delivery catheter 158. Asdescribed above, the tissue covering 154 desirably includes a plurality,typically three, of rectangular panels that are sewn together and thensewn to a cloth covering surrounding each of the struts (not shown). Theresulting structure of the coapting element 150 is compressible, thoughthe inner foam cylinder 156 expands in its relaxed configuration toprovide a generally continuous curved outer surface for good contactwith the surrounding heart valve leaflets.

FIG. 18 illustrates one technique for compressing the coapting element154 for introduction into a patient's vasculature, such as into apatient's subclavian vein. A generally funnel-shaped introducer 170 hasa wide proximal end 172 and a much smaller distal end 174, with thediameter either stepping down intermittently along its length orcontinuously. By pushing the delivery catheter and ultimately thecoapting element 150 into the introducer 170 from its proximal end 172,the coapting element can be gradually compressed until it fits throughthe narrow distal end 174. The distal end 174 may be inserted directlyinto the subclavian vein, or may connect to a pre-inserted deliverysheath of approximate the same diameter.

FIGS. 19 and 20 illustrate an alternative coapting element 180comprising a bell-shaped polymer member 182 held open at one end via amulti-strut frame 184. An upper or atrial collar 186 connects both tothe polymer member 182 and to a delivery catheter 30, although thepolymer member may be connected directly to the delivery catheter suchas via heat bonding. The delivery catheter 30 extends through theinterior of the polymer member 182 and rides over the anchor rail 26, asbefore. The multi-strut frame 184 includes a ventricular collar 188 thatattaches to the delivery catheter 30 and has a plurality, preferablythree, struts 190 that angle outward therefrom in a proximal or atrialdirection and terminate in small pads or feet 192. The feet 192 attachto an inner surface of a distal or ventricular reinforcing band 194 onthe bell-shaped polymer member 182. The struts 190 are resilient suchthat the feet 192 apply radial outward forces to the band 194 so as tomaintain the distal end of the polymer member 182 open.

FIG. 21 is a partial cutaway perspective view of a coapting element 180′similar to that shown in FIG. 19, but having a multi-strut frame 184′which is positioned within the bell-shaped polymer member 182. Thedelivery catheter 30 may extend just past the ventricular collar 188′ orfarther down into the ventricle as shown, such as to provide anexpansion balloon to assist in guiding the anchor rail 26 to a properanchoring position, as will be described below.

Both the coapting elements 180 and 180′ include relatively square closedends 196 of the polymer members 182, 182′. This is believed to bebeneficial to avoid elongated narrow internal spaces where blood mightstagnate and perhaps coagulate. A preferred material for the polymermembers 182, 182′ is a polycarbonate urethane (Carbothane from Lubrizol,Bionate from DSM, ChronoFlex from Advansource) which has extremely gooddurability over long periods of time, as opposed to materials such asNylon used for typical catheter balloons. Alternatively, a polycarbonatesilicone may also be used. In one embodiment, the outside diameter ofthe polymer members 182, 182′ is about 10 mm, while the inside diameterof the neck that attaches to the delivery catheter 30 is about 0.10inches (2.54 mm), and the constant diameter tubular portion is around 25mm.

FIGS. 22A-22G illustrates an exemplary assembly sequence for thecoapting element 180 and 180′ of FIGS. 19 and 21. First, a polycarbonateurethane balloon 198 having substantially square ends seen in FIG. 22Ais cut to length to result in the open-ended polymer member 182 in FIG.22B. Subsequently, a band 184 of polymer reinforcing material is hebonded to the open end of the polymer member 182. The reinforcingmaterial may be made of the same material as the polymer balloon but ina thicker extrusion. In one embodiment, the reinforcing band 192 is alsoradiopaque to provide visibility of the open end of the device.Subsequently, as seen in FIG. 22D, a neck portion of the polymer member182 is heat bonded to the delivery catheter 30, or via an atrial collaras shown in FIGS. 19 and 21. FIGS. 22E and 22F show attachment of thefeet 192 of the frame 184 to the reinforcing band 194. The feet 192 maybe attached in a number of ways, including heat bonding, adhesive, oreven via sutures. FIG. 22G shows a version where small sutures 199 areused to secure the feet 192 of the frame 184 to the band 194.

FIG. 23A is a perspective view of another coapting element 200 having anouter biocompatible tubular cover 202 mounted to an internal multiplestrut frame 204 and enclosing a compressible member 206 such as foamtherein. In a preferred embodiment, the tubular cover 202 comprisesbioprosthetic tissue, such as bovine pericardial tissue, although otherbiocompatible materials such as the polycarbonate urethane describedabove could be used. FIG. 23B is an end view of the coapting element 200illustrating the annular compressible member 206 surrounding the centraldelivery catheter 30, and showing the inset position of a plurality oflongitudinal struts 208 that make up the frame 204. The deliverycatheter 30 slides over the anchoring rail 26. As seen in FIG. 23A, theframe 204 includes an atrial collar 210 from which the struts 208 extendoutward and then longitudinally approximately the entire length of thecoapting element 200. The struts 208 are not joined at the distal end soas to be cantilevered from the collar 210. The collar 210 may attach viaa snap-fit to a distal coupler 212 connected to the delivery catheter30, much like the coupling sleeve 121 and distal coupler 122 describedabove with respect to FIG. 13.

FIGS. 24A-24C and 25A-25B illustrate a number of components forming thecoapting element 200. A subassembly of the frame 204 is shown secured tothree panels 214 that make up the tubular cover 202. In particular, theframe 204 defines a tripod shape with three struts 208 each of whichextends along and defines a junction between adjacent panels 214. Thecoapting element 200 is relatively flush and cylindrical on its outersurface, with the struts 208 being inset therefrom. FIG. 24B shows theframe 204 isolated with fabric tubes 216 sewn to the longitudinalportion of the struts 208. FIG. 24C is a detail of the junction betweenthe struts 208 and adjacent panels 214, wherein each panel includes aninwardly-directed edge which flanks the strut and is secured thereto viaa number of sutures 218. The inset struts 208 and seam between thepanels 214 are received in longitudinal outer grooves 219 formed in thecompressible member 206, as seen in FIGS. 25A and 25B. As mentionedthere are preferably three struts 208, but more or less could also beused. Furthermore, the compressible member 206 as an overall cylindricalouter profile, which substantially defines the final shape of thecoapting element 200, but other cross-sectional shapes such as oval orrounded triangular may also be utilized.

As mentioned, the panels 214 of the tubular cover 202 are desirablybioprosthetic tissue, such as bovine pericardium. In a preferredembodiment, a smooth side of the pericardium is placed facing outward soas to render the exterior of the coapting element 200 smooth as well. Asis well known, pericardium typically has a smooth side and a fibrous orrough side. The frame 204 is desirably highly flexible, such as beingformed of Nitinol. The resulting coapting element 200 is highlycompressible, thus responding to the forces imparted thereon by thesurrounding valve leaflets and easily conforming so as to best preventregurgitation.

FIG. 26A shows another coapting element 220 assembled, while FIG. 26Bshows the individual components thereof exploded. The coapting element220 includes an outer tubular cover 222 surrounding a porouscompressible member 224, and has a proximal frame 226 connected betweena proximal end of the tubular cover and a delivery catheter 30. Thetubular cover 222 is desirably formed of a polycarbonate urethane. Theframe 226 may be similar to those described above, having atripod-shaped series of struts that terminate in feet 228 attached to areinforcing or radiopaque band 230. The porous compressible number 224is desirably formed of an open cell foam which enables a small amount ofblood flow therethrough. An open cell foam polycarbonate urethaneprovided by Biomerix of Fremont, Calif. may be desirable. Permittingslight blood flow through the coapting element 220 may help preventstagnation and possible coagulation. Alternatively, the innercompressible member 224 may be a blood-impermeable foam, or an open cellfoam covered with an impermeable layer.

FIGS. 27A and 27B are assembled and exploded views of a coapting element230 similar to that in FIGS. 26A and 26B but wherein an outer cover 231is bell-shaped with a closed ventricular end 232 and no supportingframe. The outer cover 231 is desirably a polycarbonate urethane, andpreferably includes a radiopaque band 233 surrounding its proximal oratrial end.

FIG. 28 shows a coapting element 234 with an outer generally bell-shapedcover 235 surrounding an annular compressible member 236 mounted aroundan inner catheter 237 having perforations 238 for adding and removingair from the compressible member. As before, the inner catheter 237slides over a flexible rail 26. The flow arrows in FIGS. 29A and 29Bshow the injection and aspiration of air, respectively, from the innercatheter 237 to and from the compressible member 236, which is desirablyan open cell foam. In this way, the size of the coaptation element 234may be reduced for delivery and increased after implant. The cover 235thus functions something like a balloon, and is desirably formed ofCarbothane. The catheter 237 is also made of Carbothane so that thedistal and proximal necks of the cover 235 can easily be heat bondedthereto for a good seal, and is desirably reinforced to provide goodinner support for the pressures generated within the cover 235.

FIG. 30 is a perspective view of a still further coapting element 240having an outer bell-shaped cover 242 with a plurality of flow throughholes 244 on an otherwise closed atrial end 246. A flexible frame 248including a tripod of struts 250 maintains the distal or ventricular endopen. FIGS. 31A and 31B show alternative hole patterns, which should notbe considered limiting. For example, a circular array of round holes 244as in FIG. 31A may be provided, or the pattern may be a regulardistribution of non-circular such as rectangular through holes 254 as inFIG. 31B. The through holes 244, 254 are intended to permit a smallamount of seepage through the otherwise closed end 246 of the coaptingelement 240, thus helping to avoid stagnation and coagulation of theblood.

FIGS. 32A-32B illustrate a regurgitation reduction device 280 positionedin the right atrium/right ventricle having a three-sided frame 282 as acoaptation element, and FIGS. 33A and 33B show greater detail of thecoaptation element. FIG. 32A shows the heart in diastole during whichtime venous blood flows into the right ventricle between the opentricuspid valve leaflets and the three-sided frame 282. In the systolicphase, as seen in FIG. 32B, the tricuspid leaflets close around thecompressible frame 282, thus coapting against the frame and eliminatingopenings to prevent regurgitation.

FIG. 33B shows the desirably three-sided radial profile of the frame282, with three relatively flat convex sides 284 separated by roundedcorners 286. This rounded triangular shape is believed to faithfullyconform to the three tricuspid leaflets as they close, this betterpreventing regurgitation. Moreover, the frame 282 is desirablyunder-filled with fluid so that it can be compressed and deformed by theleaflets. FIG. 33A also shows a preferred longitudinal profile of theframe 282, with an asymmetric shape having a gradually overalllongitudinal curvature 287 and an enlarged belly region 288 just distalfrom a midline. The shape resembles a jalapeno pepper. Due to thecurvature of the path from the superior vena cava SVC down through thetricuspid valve TV and into the right ventricle RV, the overallcurvature 287 of the frame 282 helps position a mid-section moreperpendicular to the tricuspid valve leaflets, while the unevenlongitudinal thickness with the belly region 288 is believed to moreeffectively coapt with the leaflets.

As an alternative to being fluid-filled, the frame 282 may have aplurality (e.g. >20) of very thin and highly flexible struts (not shown)that connect between top and bottom collars, for instance. The strutsthus relocate independently of one another, which allows leaflet motionto deform the highly compliant frame 282 into whatever shape bestconforms to the remaining orifice. Since segments of the frame 282adjacent areas with high leaflet mobility would be compressed, thecoaptation element could be dramatically oversized with respect to theregurgitant orifice size in order to maintain coaptation in commissuralregions

FIGS. 34 and 35 are radial section views through the coaptation element280 of FIG. 33A showing two different possible configurations. In afirst embodiment in FIG. 34, the coaptation element 280 is hollow orfilled with a fluid such as saline. In a second embodiment in FIG. 35,the coaptation element 280 has a compressible member 290 interposedbetween an outer cover 284 and the delivery catheter 30. Thecompressible member 290 may be an open cell polycarbonate urethane foam,for example. Likewise, the outer cover may be a polycarbonate urethane.The latter configuration eliminates the potential for the fluid-filledframe 282 to deflate, thus maintaining good coaptation function forextended periods.

One potential challenge of a static coaptation element within thetricuspid valve annulus could be diastolic stenosis, i.e. restriction ofblood flow from the right atrium to the right ventricle during diastole.In patients with an excessively large regurgitant orifice, sizing thedevice for proper coaptation during systole could have consequences indiastole. To address this issue, a coaptation element 300 could beattached to a flexible metallic spring 304 connected to anchor 302,therefore allowing the coaptation element to move in and out of theannulus plane during systole and diastole, respectively (see FIGS. 36Aand 36B). During systole, as in FIG. 36B, the pressure gradient as wellas fluid inertial forces would cause the spring 304 to extend, andduring diastole the spring constant as well as fluid inertial forceswould cause the spring to contract. Instead of just one spring distal tothe coaptation element, a spring could be placed on both sides in orderto increase mobility. Alternatively, with one spring, the “home”position of the coaptation element (i.e. with no force from the springor fluid) could either be at the annulus plane or below the annulusplane in the RV. In the former case, inertial forces of diastolic flowwould be required to move the coaptation element down out of the annulusplane during diastole, and in the latter case, both inertial forces ofsystolic flow and forces from the RV/RA pressure gradient could move thecoaptation element up to the annulus during systole.

Anchors and Alternative Anchor Placement:

The following list of embodiments presents additional design ideas forthe catheter railing and anchoring system:

FIGS. 37 and 38 are views of alternative anchoring members utilizingconical coil springs. One potential challenge of some proposed helicalanchors is the limited surface area on which the anchor can “grab”tissue given its short cylindrical length (2 mm). In order to maximizethe area of tissue contact over the 2 mm length of the anchor, amodified helical anchor 310 could be developed which has a conicalshape, i.e. a circular cross-section of increasing size towards thedistal end. The conical spring anchor 310 could be provide at the end ofan anchor rail 312, as previously described. Such an anchor design couldincrease retention force by increasing the cross-sectional area ofcontact between the anchor coil and the tissue. Additionally, as theinitial cut of the anchor 310 into the tissue would be largest followedby decreasing coil diameter as the anchor is screwed in, the anchorcould effectively “cinch” in a volume of tissue into a compacted space.Such a feature could potentially minimize the risk for anchor tear-outby increasing the local tissue density at the anchor site. The conicalspring 310 could be comprised of any shape memory material capable ofcollapsing or wrapping down to a smaller constant diameter to fitthrough a catheter lumen, then capable of expanding to the naturalconical shape upon exiting the delivery sheath into the RV.

Alternatively, a conical anchor 314 could be connected via an elongatedhelical section 316 at its proximal end designed to remain in the RV(not screwed into the tissue but directly next to it), such as shown inFIG. 38. The elongated helical section 316 provides shock absorptioncapabilities against compressive/tensile stresses, thus reducingtear-away stresses on the RV apex, and also flexibility capabilitiesunder bending stresses.

Using helical structures for anchoring the devices described herein inthe right ventricle holds a number of advantages (e.g. ease of delivery,acute removability, minimal tissue damage, etc.). However, one potentialchallenge could be the tendency of a helical structure to “unscrew”itself out of the tissue, either acutely or over time due to thecontractile motions of the ventricle. To address this issue, an anchorsystem in FIG. 39 includes concentric corkscrew anchors; an inner anchor320 at the end of an inner tube 322, and an outer anchor 324 on the endof an outer tube 326. FIGS. 39A-39C illustrate steps in installation ofthe anchoring device, in which first the inner anchor 320 having aclockwise orientation is screwed into the tissue. Next, the slightlylarger second anchor 324, having a counterclockwise orientation, and itstube 326 slide over the first anchor 320 and tube 322 and screws intothe tissue in the opposite direction. Finally, the two anchors could befixed together with a locking mechanism (e.g., pin-through-hole style).The resulting structure would resist unscrewing out of the tissue, sinceeach helical coil opposes the twisting motion of the other.

FIG. 40 shows another configuration with a helical corkscrew-type anchor330 on the end of a tube 332, and a pair of struts 334 that may beindependently expelled from the distal end of the tube into contact withthe tissue surrounding the anchor. Rather than screwing in a secondrelatively similar anchor in the opposite direction to preventtwist-out, the struts 334 pass through the tube lumen and extendoutwards in an L-shaped manner to provide an anti-rotation anchor to thedevice. These struts 334 should be thick enough to press against the RVapex tissue and apply friction thereto to prevent twisting motion of theanchor 330.

In an alternative approach to enabling fine control over the position ofthe coaptation element within the valve plane, as seen in FIG. 41, aseries of two or more anchors 340 could be deployed in various areas ofthe RV (including possibly the papillary muscles). The attached anchorrails 342 could all extend through a lumen of the coaptation element(not shown). In order to re-position the coaptation element, the tensionon any given anchor rail 342 could be altered independently at theaccess site, thus increasing or decreasing the degree of tethering onthe coaptation element in a certain direction. For example, to move thecoaptation element to a more posterior position within the valve, theanchor rail 342 corresponding to the more posterior anchor 340 could bepulled more taught. Once the desired position is achieved, the relativelengths of all the anchor rails could be fixed with respect to thecoaptation element catheter via a locking or clamping mechanism at theproximal end of the device. The anchor rails referenced previously couldinstead be cable wires (with no lumen) in order to minimize the profileof the coaptation element catheter given that multiple anchorattachments will need to fit within the device inner lumen. In order tofacilitate easily distinguishing which cable attaches to which anchor,the catheter could contain a series of lumens (at least two) for cablewires which would be labeled based on anatomical location of thecorresponding anchor. Therefore, at the proximal end of the device, itwould be clear which cable would be required to pull in order totranslate the coaptation element in a certain direction.

FIGS. 42A and 42B show operation of a centering balloon 350 that helpsensure proper positioning of an anchor 352 at the apex of the rightventricle. A series of experiments in a bench-top pulsatile flow modelwith porcine hearts has emphasized the importance of RV anchor positionfor achieving central location of the coaptation element within thevalve. Thus, it may be necessary to utilize an accessory catheter 354for the present device to help facilitate delivery of the anchor 352 tothe ideal location within the ventricle, or the centering balloon 250may be mounted on the distal end of the delivery/anchoring catheteritself. One such approach relies on using the annulus itself to guidethe anchor shaft. For instance, a perfusion balloon 350 large enough tofill the entire valve could be inflated within the tricuspid annulus,therefore counting on opposition between the annulus and the perfusionballoon to orient the angle of the catheter lumen directly normal to andthrough the center of the valve plane. FIG. 42A shows the unwantedposition of the anchor 350 before balloon inflation, while FIG. 42Bshows the desired positioning at the RV apex after the balloon 350 isinflated. At this point, the anchor shaft would pass through the lumenof the perfusion balloon catheter (either an accessory catheter or thedelivery catheter itself), which is oriented so as to guide the anchorto the ideal central location along the anterior-posterior axis of theRV apex. The centering balloon 250 allows the delivery system to trackinto the RV while avoiding chords and ensuring central placement ratherthan between leaflets.

FIG. 43 illustrates a step in directing an anchoring catheter 360 to theapex of the right ventricle using an L-shaped stabilizing catheter 362secured within a coronary sinus. This configuration addresses thechallenge of guiding the anchor delivery. The catheter 362 is capable ofdeflecting into an L-shape, and would be advanced from the SVC, into theright atrium, then into the coronary sinus, which would provide astabilizing feature for the guide catheter. The catheter 362 could bemaneuvered further in or out of the coronary sinus such that the “elbow”of the L-shape is positioned directly above the center of the valve,then the anchor catheter 360 could be delivered through the lumen of theguide catheter 362 and out a port at the elbow of the L-shape. Atemporary stiffening “stylet” (not shown) could be used through theanchor rail lumen to ensure the anchor is delivered directly downwardsto the ideal point at the RV apex.

If any of the previously described anchoring options involving anycombination of the RV, SVC, and IVC prove to be undesirable, thecoaptation element could instead be anchored directly to the annulus. Asshown in FIG. 44, a series of at least two anchors 370 (similar to thehelical RV anchors) could be deployed into the fibrous portion of theannulus, then cables or stabilizing rods 372 could be used to hang orsuspend the coaptation element 374 within the annulus plane. Eachsupport cable or rod 372 would need to be relatively taught, so as toprevent motion of the device towards the atrium during systole. Anynumber of supports struts greater than two could be utilized. Thesupport cables for suspending the coaptation element from the annuluscould be relatively flexible, and thus the position and mobility of thedevice would be altered via tension in the cables. Alternatively, thesupport elements could be relatively stiff to decrease device motion,but this would require changing anchor position to reposition thecoaptation element. Although an anchor 376 to the RV apex is shown, thedual annulus anchors 370 might obviate the need for a ventricularanchor.

The general concept of cylindrical stent-based anchor mechanisms for thedevice could be applied in other structures near the tricuspid valvesuch as the coronary sinus. For instance, FIG. 45 illustrates anadjustable stabilizing rod 380 mounted on a delivery catheter 382 andsecured to an anchor 384 within the coronary sinus. The stabilizing rod380 attaches via an adjustable sleeve 386 to the catheter 382, thussuspending the attached coapting element 388 down into the regurgitantorifice. A sliding mechanism on the adjustable sleeve 386 permitsadjustment of the length between the coronary sinus anchor 384 and thecoaptation device 388, thus allowing positioning of the coaptationelement at the ideal location within the valve plane. For furtherstability, this coronary sinus anchoring concept could also be coupledwith a traditional anchor in the RV apex, as shown.

While venous access to the RV through the subclavian vein and into thesuperior vena cava is a routine procedure with minimal risk forcomplications, the fairly flat access angle of the SVC with respect tothe tricuspid valve plane presents a number of challenges for properorientation of the present coaptation element within the valve. If thecatheter were not flexible enough to achieve the correct angle of thecoaptation element with respect to the valve plane by purely passivebending, a flex point could be added to the catheter directly proximalto the coaptation element via a pull wire attached to a proximal handlethrough a double lumen extrusion. For instance, FIG. 46 illustrates analternative delivery catheter 390 having a pivot joint 392 just abovethe coapting element 394 for angle adjustment. If a given combination ofSVC access angle and/or RV anchor position resulted in a crookedcoaptation element within the valve plane, the catheter 390 could bearticulated using the pull wire (not shown) until proper alignment isachieved based on feedback from fluoroscopic views.

Additional flex points could be added to further facilitate control ofdevice angle, e.g. another flex point could be added distal to thecoaptation element 394 to compensate for the possible case that the RVwall angle (and thus the anchor angle) is skewed with respect to thevalve plane. This would require an additional independent lumen withinthe catheter body 390 to facilitate translation of another pull wire tooperate the second flex feature. Alternatively, if a single flex pointproximal to the coaptation element were determined to be sufficient fororienting the device, and if the catheter were rigid enough to resistthe forces of systolic flow, the section 396 of the device distal to thecoaptation element could be removed all together. This would leave onlyone anchoring point for the device in the SVC or subcutaneously to thesubclavian vein. Also, as an alternative to an actively-controlled flexpoint, the catheter could contain a shape-set shaft comprised of Nitinolor another shape memory material, which would be released from a rigiddelivery sheath into its “shaped” form in order to optimize device anglefrom the SVC. It could be possible to have a few catheter options ofvarying pre-set angles, yet choose only one after evaluation of theSVC-to-valve plane angle via angiographic images.

Instead of using an active mechanism within the catheter itself tochange its angle, another embodiment takes advantage of the surroundinganatomy, i.e. the SVC wall. FIGS. 47A and 47B show two ways to anchorthe delivery catheter 400 to the superior vena cava SVC for stabilizinga coapting element 402. For example, a variety of hooks or anchors 404could extend from a second lumen within the catheter 402 with theability to grab onto the SVC wall and pull the catheter in thatdirection (FIGS. 47A and 47B). Alternatively, a stiffer element couldextend outwards perpendicular to the catheter axis to butt up againstthe SVC wall and push the catheter in the opposite direction. Forespecially challenging SVC geometries, such a mechanism couldpotentially be useful for achieving better coaxial alignment with thevalve.

FIGS. 48A and 48B show an active regurgitation reduction device 410having pull wires 412 extending through the delivery catheter 414 foraltering the position of the coapting element 416 within the tricuspidvalve leaflets. If the coapting element 416 is located out of the middleof the valve leaflets such that it does not effectively plug anyregurgitant jets, which can be seen on echocardiography, then one of thepull wires 412 can be shortened or lengthened in conjunction withrotating the catheter 414 to reposition the coapting element 416, suchas seen from FIG. 48A to FIG. 48B.

Although pacemaker leads are frequently anchored in the right ventriclewith chronic success, the anchor for the present device would seesignificantly higher cyclic loads due to systolic pressure acting on thecoaptation element. Given that the right ventricle wall can be as thinas two millimeters near the apex and the tissue is often highly friablein patients with heart disease, anchoring a device in the ventricle maynot be ideal. An alternative anchoring approach could take advantage ofthe fairy collinear orientation of the superior and inferior vena cava,wherein, as seen in FIG. 49, two stent structures 420, 422 wouldeffectively “straddle” the tricuspid valve by expanding one in thesuperior vena cava and the other in the inferior vena cava. Thecoaptation element 424 would then hang down through the tricuspid valveplane from an atrial shaft 426 attached to a connecting wire or rod 428between the two caval stents 420, 422. In order to resist motion of thecoaptation element under systolic forces, the shaft 426 from which thecoaptation element 424 hangs would be fairly rigid under compressive andbending stresses. The coaptation element 424 would desirably bepositioned within the valve using a sliding mechanism along theconnecting rod 428 between the two caval stents.

The coaxial orientation of the SVC and IVC could also be leveraged fordelivering an anchor into the RV. A delivery catheter could be passedthrough the SVC into the IVC, and a “port” or hole off the side of thedelivery catheter could be aligned with the center of the valve. At thispoint, the anchor could be passed through the lumen of the deliverysystem and out the port, resulting in a direct shot through the centerof the annulus and to the RV wall in the ideal central anchor location.

This concept could potentially be applied to the left side of the heartas well, to address mitral regurgitation. A coaptation element couldreside between the mitral valve leaflets with anchors on both theproximal and distal ends: one attaching to the septal wall, and theother anchoring in the left atrial appendage. The septal anchor could bea helical or hook-style anchor, whereas the left atrial appendage anchorcould be an expandable metallic structure with a plurality of struts orwireforms designed to oppose against the appendage wall and providestability to the coaptation element.

Pacemaker leads frequently lead to tricuspid regurgitation (TR) bypinning a leaflet or interfering with leaflet mobility. In thisparticular embodiment, a device, a gap filler, is designed to beintroduced over the offending pacemaker lead (of course, applicable alsoto those with organic tricuspid regurgitation and a pacemaker lead inplace). The invention is a tricuspid regurgitant volume gap filler thatis placed over the existing pacemaker lead via a coil wound over thelead or a slit sheath approach, which acts like a monorail catheter. Thegap filler catheter is advanced over the pacemaker lead and thetricuspid regurgitation is evaluated by echo while the monorail gapfiller device is placed into the regurgitant orifice. The proximal endof the gap filler allows for crimping and truncating the catheterpost-balloon inflation or gap filler deployment. This mates the monorailgap filler to the pacemaker lead at the proper position within thetricuspid valve.

FIGS. 50-51 are schematic views of a coapting element 430 mounted forlateral movement on a flexible delivery catheter 432 that featurescontrolled buckling. It is challenging to reposition the coaptationelement 430 from an off-center location to the ideal central locationwithin the valve plane, given a fixed angle from the SVC and a fixedanchor position in the RV. The device catheter 432 could be comprised ofa fairly stiff shaft except for two relatively flexible regions 434, 436directly proximal and distal to the coaptation element section. Thefarthest distal section of the coaptation catheter 432 could be lockeddown relative to the anchor rail over which it slides, and then thecatheter 432 could be advanced distally thus compressing it and causingthe two flexible sections 434, 436 to buckle outwards and displace thecoaptation element laterally with respect to the catheter axis (see FIG.50C). At this point, the user could employ a combination of sliding androtating of the catheter to reposition the coaptation element 430 withinthe valve using short-axis echo feedback. Instead of locking the distalend of the catheter onto an anchor rail before adjustment, if thecatheter were comprised of multiple lumens, the outer lumen could slidedistally relative to the inner lumen, thus producing the same bucklingeffect.

In another embodiment, not shown, an alternative approach could be torely on the contractile motion of the heart to move a tapered coaptationelement in and out of the tricuspid valve plane. A tapered coaptationelement, with a smaller cross-section proximally (towards the atrium)and larger cross-section distally (towards the ventricle), would beattached to a rigid distal railing and anchor. During systoliccontraction, the anchor and therefore the attached coaptation elementwould move towards the annulus, thus allowing the tricuspid leaflets tocoapt around the larger cross-section of the device. Conversely,diastolic expansion of the RV would bring the anchor and therefore thecoaptation element downwards such that the smaller cross-section of thedevice is now within the annulus plane, thus minimizing diastolicstenosis. A combination of a tapered element with a spring could be usedif RV wall motion towards the annulus is not sufficient to move thedevice.

While the foregoing is a complete description of the preferredembodiments of the invention, various alternatives, modifications, andequivalents may be used. Moreover, it will be obvious that certain othermodifications may be practiced within the scope of the appended claims.

What is claimed is:
 1. A method of reducing regurgitation through nativeleaflets of an atrioventricular heart valve, comprising: advancing aguide wire from an atrium and across the heart valve to a ventricle;advancing a delivery catheter over the guide wire, the delivery catheterhaving an internal lumen and a distal end portion, the catheter beingmade of material suitable for long-term implant in the human body, thecatheter having a valve leaflet coaptation element mounted over thedistal end portion, the coaptation element having an outer cover, and aflexible inner support comprising a porous compressible foam membersubstantially filling the cover such that the outer cover mayalternately deform inward and spring outward, wherein the coaptationelement is radially compressed to a compressed configuration duringadvancement of the catheter, the coaptation element being made ofmaterial suitable for implant in the human body; positioning thecoaptation element within the heart valve; permitting the coaptationelement to radially expand from the compressed configuration to anenlarged configuration for filling a gap between the native leaflets ofthe heart valve, and wherein the foam member is in fluid communicationwith blood flow past the heart valve so that blood may enter pores inthe foam member; and fixing a position of the coaptation elementrelative to the heart valve and thereby reducing regurgitation throughthe native leaflets of the heart valve.
 2. The method of claim 1,wherein the catheter has a proximal anchor adapted to anchor into tissuelocated at one of either an annulus of the heart valve, the inferiorvena cava, or the right atrium and has a length sufficient to extendfrom the proximal anchor to the heart valve.
 3. The method of claim 1,wherein the step of advancing the delivery catheter includes introducingthe catheter into the subclavian vein and advancing the catheter throughthe superior vena cava to the right atrium and then to the tricuspidvalve.
 4. The method of claim 1, further including an elongated flexibleanchor rail made of material suitable for implant in the human body andhaving a distal anchor, and the method includes advancing the anchorrail over the guide wire and across the heart valve to the ventricle,and anchoring the anchor within the ventricle, the step of advancing thedelivery catheter includes advancing the catheter over the anchor rail,and the step of anchoring a position of the coaptation element includesanchoring the catheter relative to the anchor rail.
 5. The method ofclaim 4, further including a locking collet on a proximal end of thecatheter for securing the axial position of the catheter on the anchorrail, the locking collet being made of material suitable for implant inthe human body.
 6. The method of claim 1, wherein the coaptation elementdefines an asymmetric shape along its longitudinal axis having anenlarged belly region just distal from a midline relative to a narrowerproximal end.
 7. The method of claim 1, wherein the coaptation elementhas a rounded triangular shape in radial section.
 8. The method of claim1, wherein the outer cover is formed of polycarbonate urethane, whereinthe catheter is also made of polycarbonate urethane and distal andproximal necks of the outer cover are heat bonded to the catheter. 9.The method of claim 1, wherein the foam member extends substantially thelength of the outer cover.
 10. The method of claim 9, wherein the outercover is open at both ends to expose the foam member to blood.
 11. Amethod of reducing regurgitation through native leaflets of anatrioventricular heart valve, comprising: advancing a guide wire from anatrium and across the heart valve to a ventricle; advancing a deliverycatheter over the guide wire, the delivery catheter having an internallumen and a distal end portion formed with perforations in fluidcommunication with the lumen, the catheter made of material suitable forlong-term implant in the human body, the catheter having a valve leafletcoaptation element mounted over the distal end portion, the coaptationelement having an outer cover secured on proximal and distal of catheterto provide a closed chamber around the perforations, and a flexibleinner support comprising a porous compressible foam member substantiallyfilling the cover such that the outer cover may alternately deforminward and spring outward, wherein the coaptation element is radiallycompressed to a compressed configuration during advancement of thecatheter, the coaptation element being made of material suitable forimplant in the human body; positioning the coaptation element within theheart valve; permitting the coaptation element to radially expand from acompressed configuration to an enlarged configuration for filling a gapbetween the native leaflets of the heart valve; and fixing a position ofthe coaptation element relative to the heart valve and thereby reducingregurgitation through the native leaflets of the heart valve.
 12. Themethod of claim 11, wherein the catheter has a proximal anchor adaptedto anchor into tissue located at one of either an annulus of the heartvalve, the inferior vena cava, or the right atrium and has a lengthsufficient to extend from the proximal anchor to the heart valve. 13.The method of claim 11, wherein the step of advancing the deliverycatheter includes introducing the catheter into the subclavian vein andadvancing the catheter through the superior vena cava to the rightatrium RA and then to the tricuspid valve.
 14. The method of claim 11,further including an elongated flexible anchor rail made of materialsuitable for implant in the human body and having a distal anchor, andthe method includes advancing the anchor rail over the guide wire andacross the heart valve to the ventricle, and anchoring the anchor withinthe ventricle, the step of advancing the delivery catheter includesadvancing the catheter over the anchor rail, and the step of anchoring aposition of the coaptation element includes anchoring the catheterrelative to the anchor rail.
 15. The method of claim 14, furtherincluding a locking collet on a proximal end of the catheter forsecuring the axial position of the catheter on the anchor rail, thelocking collet being made of material suitable for implant in the humanbody.
 16. The method of claim 11, wherein the coaptation element definesan asymmetric shape along its longitudinal axis having an enlarged bellyregion just distal from a midline relative to a narrower proximal end.17. The method of claim 11, wherein the coaptation element has a roundedtriangular shape in radial section.
 18. The method of claim 11, whereinthe outer cover is formed of polycarbonate urethane, wherein thecatheter is also made of polycarbonate urethane and distal and proximalnecks of the outer cover are heat bonded to the catheter.
 19. The methodof claim 11, wherein the compressible foam member extends substantiallythe length of the outer cover.